The present invention relates generally to fuel vapor emission control in vehicles having internal combustion engines. More particularly, the invention relates to a system and method for removing hydrocarbons from the air induction system of an internal combustion engine.
Vehicles having internal combustion engines are known to release unwanted hydrocarbons during refueling and cold starting of the vehicle engine. During refueling, for example, unburned fuel vapors containing such hydrocarbons are released from the vehicle""s fuel tank after the fuel tank cap is removed. Similarly, because a stoichiometric air/fuel ratio is difficult to achieve during cold start, a higher proportion of unburned fuel vapor is delivered to the vehicle""s catalytic converter thus resulting in higher concentration of hydrocarbons released into the atmosphere.
As such, vehicles have been designed to include various systems and methods for minimizing the release of fuel vapor emissions during vehicle start-up and refueling. Examples of such systems are disclosed in U.S. Pat. Nos. RE 36,737, 5,924,410 and 5,957,114, which are all assigned to the assignee of the present invention.
Such systems, for example, are not helpful for controlling the release of unburned fuel vapors from combustion chambers and/or fuel ports during engine operation. One such situation occurs after evaporative emissions migrate or xe2x80x9cleakxe2x80x9d back in an xe2x80x9cupstreamxe2x80x9d direction from the combustion chambers and/or fuel ports of the engine through a corresponding intake manifold and throttle valve. Any emissions migrating back through the intake valves are then subject to release into the atmosphere.
Accordingly, and further in light of increasingly stringent environmental standards, the inventor herein has recognized the need to minimize the amount of unburned fuel vapors migrating back into the air induction system of an internal combustion engine.
The aforedescribed limitations and inadequacies of conventional fuel evaporative emission controls systems and methods are substantially overcome by the present invention, in which a method is provided for minimizing evaporative fuel emissions of a vehicle having an internal combustion engine. The method includes the step of storing fuel vapors emanating from the engine to prevent the migration of the fuel vapors in an xe2x80x9cupstreamxe2x80x9d direction from the engine through the throttle valve assembly. Preferably, the stored fuel vapors are released back into the engine""s air induction system during engine operation. During engine start-up, for example, the amount of fuel required for start-up can be adjusted in order to take into account the release of the fuel vapors into the air induction system of the engine.
An advantage of the above method is that the amount of fuel evaporative vapors accumulated in the engine""s air induction system is reduced, thereby preventing the release of residual gases, e.g., hydrocarbons, into the atmosphere. By storing and then releasing the evaporative emissions at an appropriate time, such a system is especially advantageous for compliance with government fuel emissions standards. The amount of stored fuel vapor released back into the engine""s air induction system can then be used to xe2x80x9ccalibrate-outxe2x80x9d a corresponding amount of fuel required for engine operation. For example, taking into account the amount of released fuel vapors can reduce the amount of fuel required for engine start-up. Consequently, an additional advantage is realized in that less fuel is required for engine start-up.
In accordance with a related aspect of the present invention, a corresponding system for minimizing fuel evaporative emissions is provided. The system includes a duct connected to a throttle valve assembly for providing atmospheric air to the engine and a fuel vapor absorbing material disposed on the interior of the duct for absorbing and storing the fuel emissions emanating from the engine through the intake manifold and the throttle valve assembly. Preferably, the duct is includes a first end coupled to the throttle valve assembly, and a fuel vapor absorbing material disposed on the interior for absorbing and storing the fuel emissions. The system also includes an engine controller for determining an amount of fuel to be provided to the engine and adjusting an amount of fuel provided to the engine after the stored fuel emissions are released from the material.
Still further, in accordance with yet another aspect of the present invention, an article of manufacture is disclosed for operating an internal combustion engine having a throttle valve assembly in cooperation with a corresponding intake manifold and fuel vapor absorbing material near the throttle valve assembly for absorbing and storing evaporative fuel emissions emanating from the engine through the intake manifold and the throttle valve assembly. The article of manufacture includes a computer usable medium and a computer readable program code embodied in the computer usable medium for directing the computer to perform the steps of directing the computer to perform the step steps of determining an amount of fuel to be provided to the engine and adjusting an amount of fuel provided to the engine after the stored evaporative fuel emissions are released from the material.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.